1. Field of the Invention
This invention relates generally to magnetic devices for reading from or writing onto a magnetic storage medium and methods of fabricating the same, and more particularly, but not by way of limitation, to thin film magnetic heads which include two magnetic pole elements having offset portions and to methods of manufacturing the same.
2. Description of the Prior Art (Prior Art Statement)
The following statement is my prior art statement in compliance with the guidance and requirements of 37 C.F.R. 1.56, 1.97 and 1.98.
U.S. Pat. No. 4,151,574 issued to Gerkema et al. discloses a type of magnetic head having a substrate 1 which includes a groove 2 wherein a thin film magnetic field-sensitive element 4 is formed solely on one side wall of the groove.
U.S. Pat. No. 4,092,688 issued to Nomura et al. discloses a multi-track thin film magnetic head which, as shown in FIG. 6 of the patent, proposes a sloped groove substrate which is completely filled with a non-magnetic material 31 on top of which various other layers are deposited.
U.S. Pat. No. 3,795,954 issued to Alex et al. discloses in FIG. 1 of the patent a channel-shaped ferrite piece 10 which receives deposition throughout the grooved surface. This deposition is proposed to be of non-magnetic metal layers 20 and 22 and glass layer 28. The glass layer 28 is joined to a glass layer 30 which is carried by a flat ferrite rectangular layer 12.
U.S. Pat. No. 3,672,043 and U.S. Pat. No. 3,564,521, both issued to Trimble et al., disclose a miniature magnetic head. FIG. 2 of each of these patents discloses a substrate 25 having recesses 25a, 25b, and 25c wherein a thin layer 35 of high permeability magnetic material is deposited.
As shown by the preceding references, there is a need for thin film magnetic heads. This need exists because thin film heads reduce the physical size of magnetic recording and playback apparatus and permit better utilization of the available storage area of a recording medium.
In addition to the basic need for thin film magnetic heads, there is the need for such heads to have a structure which reduces cracking and other fabrication defects in the layers of materials applied to the substrate. In particular, as is shown in the cited references and is generally known in the art, in the batch fabrication of thin film magnetic heads the front and back gap regions of the magnetic films have had steep slopes due to the necessary build-up of the intermediate layers on top of the flat surface of the substrate. These slopes have presented a severe coverage problem for, in particular, the top pole magnetic film. This is particularly troublesome when the top pole magnetic film is put on by a vacuum technique such as sputtering or evaporation because the magnetic film tends to crack due to the steepness of the slope along which the layer extends. This cracking reduces the quality or precludes the use of such defective heads and thus creates a need for a type of thin film magnetic head and method of making the same which improves the quality by reducing or eliminating the cracking problem.
Still another need is to provide a thin film magnetic head having pole elements which are symmetrically placed around the conductor elements of the head. As the cited references indicate and as is generally known in the art, present heads are asymmetrical because they are constructed with various layers built on a flat surface of the substrate. Such asymmetry creates a structure having operating qualities which are inferior to those of a symmetrical structure. Thus, the need arises for a symmetrical head having improved operating characteristics.
Because of these shortcomings of the cited references, it is believed that the cited references fail to meet these needs.